.main_head{
	height:50px;
	text-align:center;
}
.main_menu{
	heihgt:50px;
}
.main_center{
	margin:0;
	padding:0;
	position:absolute;
	width: 100%;
	height: 90%;
}
.main_footer{
	text-align:center;
	height:30px;
}
.leftmenu{
	float:left;
    width:20%;
    height:100%;
}
.maincontent{
	float:left;
	width:80%;
	height:100%;
}